Energy efficiency optimization of resource allocation in hierarchical HetNets

DOBRUNA, JETA (author), Volk, Mojca (mentor)

With the rapid advancement of technology, access to wireless services has become a daily necessity. In response to this need, network densification techniques are being deployed in which low-power Base Stations (BS), also called small BSs, are introduced in the same coverage and frequency range as the macro BSs, thus introducing the concept of a heterogeneous network (HetNet). HetNets are considered the principal architectural concept in future communication networks, especially in the Fifth Generation (5G) and the Sixth Generation (6G) networks. The ultra-dense deployment of small cells in HetNets has raised serious concerns regarding interference and energy consumption. Resource allocation and user association are the main approaches used to address these challenges. Today, numerous different strategies exist, depending on the chosen approach and the optimization targets pursued. Two important interrelated targets are interference coordination and energy efficiency (EE) optimization; improved EE can significantly reduce the operator’s operational costs, and better interference coordination leads to more efficient energy consumption. However, the complexity of finding an optimal solution increases when an ultra-dense HetNet scenario is considered. The main objective of this thesis is to develop a user association and power management algorithm that follows a heuristic approach and aims to maximize energy efficiency (EE). The proposed algorithm follows a heuristic approach for associating users with the BSs and exhibits low complexity. The switch ON/OFF technique is applied to manage power consumption. By implementing this technique, the proposed algorithm turns off the BSs that do not serve any users, as well as the macro BSs that have the largest impact on the network aggregated EE. The performance of the proposed algorithm is evaluated in a reference two-tier HetNet, considering all types of interferences. To validate the performance, we compared the proposed solution with two selected benchmarking solutions based on the eICIC technique and Lagrangian dual decomposition, respectively. The simulation results show that by minimizing energy consumption, the proposed solution outperforms the two benchmarking solutions in terms of EE and average user rate.

• Language: English
• Keywords: HetNets, user association, resource allocation, power management, interference coordination, energy efficiency (EE), scalability, quality of service (QoS), heuristic approach, switch ON/OFF technique
• Work type: Doctoral dissertation
• Typology: 2.08 - Doctoral Dissertation
• Organization: FE - Faculty of Electrical Engineering
• Year: 2025
• PID: 20.500.12556/RUL-167408
• COBISS.SI-ID: 227805443
• Publication date in RUL: 20.02.2025

Secondary language

• Language: Slovenian
• Title: Optimizacija energijske učinkovitosti razporejanja virov v hierarhičnih omrežjih HetNet

Abstract

S hitrim napredkom tehnologije je dostop do brezžičnih storitev postal vsakodnevna nuja. Kot odgovor na to potrebo se v sodobnih omrežjih uporabljajo tehnike zgoščevanja omrežij, kjer v že obstoječa območja pokrivanja makro baznih postaj (angl. Base Station – BS) dodatno nameščamo bazne postaje z nizko oddajno močjo oziroma t.i. majhne bazne postaje (angl. Small BS), s čimer uvajamo t.i. koncept heterogenih omrežij (angl. Heterogeneous Network – HetNet). Omrežja HetNet predstavljajo primarno arhitekturo komunikacijskih omrežij prihodnosti, zlasti pete in šeste generacije mobilnih omrežij (angl. Fifth Generation – 5G, Sixth Generation – 6G). Vendar pa je ultra-gosto nameščanje majhnih celic v omrežjih HetNet s seboj prineslo resne izzive z vidikov upravljanja interferenc in porabe energije. Dodeljevanje virov in asociacija uporabnikov sta glavna pristopa k reševanju teh izzivov, pri čemer danes obstajajo številne strategije optimizacije zmogljivosti omrežja, ki se med seboj razlikujejo glede na izbran pristop in zasledovane optimizacijske cilje. Dva pomembna in med seboj povezana cilja sta koordinacija interferenc in optimizacija energetske učinkovitosti (angl. Energy Efficiency – EE); izboljšana EE lahko znatno zniža operaterjeve operativne stroške, boljša koordinacija interferenc pa vodi v bolj učinkovito porabo energije. Vendar pa se kompleksnost iskanja takšne optimalne rešitve bistveno poveča v primeru scenarija ultra-gostega omrežja HetNet. Glavni cilj tega doktorskega dela je razvoj algoritma za asociacijo uporabnikov in upravljanje porabe energije, ki sledi hevrističnemu pristopu in zasleduje maksimizacijo energetske učinkovitosti. Predlagan algoritem sledi hevrističnemu pristopu za asociacijo uporabnikov z baznimi postajami in izkazuje nizko stopnjo kompleksnosti. Za upravljanje porabe moči je uporabljena tehnika vklop/izklop (angl. switch ON/OFF), ki omogoča, da algoritem izklaplja bazne postaje, ki ne strežejo uporabnikov, in tiste makro bazne postaje, ki imajo največji vpliv na agregirano energetsko učinkovitost omrežja. Učinkovitost algoritma smo ovrednotili na primeru referenčnega dvonivojskega omrežja HetNet ob upoštevanju vseh tipov interferenc. Za potrebe potrditve zmogljivosti smo predlagano rešitev primerjali z dvema izbranima primerjalnima rešitvama, ki temeljita na tehniki eICIC oziroma Lagrangeovi dvojni razgradnji. Rezultati simulacij kažejo, da z zmanjšanjem porabe energije predlagana rešitev prekaša izbrani primerjalni rešitvi v smislu EE in povprečne hitrosti podatkovnega prometa.

• Keywords: HetNet, asociacija uporabnikov, dodeljevanje virov, upravljanje porabe energije, koordinacija interferenc, energetska učinkovitost (EE), razširljivost, kakovost storitve (QoS), hevristični pristop, tehnika vklop/izklop